The senator -- Republican Jon Kyl of Arizona -- is a staunch defender of the Pentagon's budget, and it's no surprise that he is protecting the military's interests.

"Over a period of several decades, the Republican position on defense spending has been perfectly clear," said Travis Sharp, a fellow at the Center for a New American Security. "That position is: more is better."

But Kyl and other defense hawks are fighting an uphill battle. After years of steady increases, the Pentagon's budget is starting to level off. The wars in Iraq and Afghanistan are winding down.

Simply put, the Pentagon budget might be reined in no matter what the super committee decides. As it usually does at the end of prolonged conflicts, Washington is starting to think about the Pentagon's mission and the size of its budget.

"This is a perfect moment to ask: 'What's the right strategy? What's the right mission? Where can we accept greater risk?' " said Gordon Adams, a professor at American University and a former Clinton administration budget official.

Overall defense spending accounts for 20% of the entire federal budget. Last year, the Pentagon spent $530 billion, without even counting war costs. Now, those numbers might be in line for a reduction.

Already, the debt ceiling deal struck by the nation's top lawmakers includes $350 billion in cuts to the defense budget over the next decade.

Kyl fears that in order to reach its overall budget target, the committee will look for even more savings in the Pentagon's budget.

But the committee will only be deciding the top line spending levels -- and won't be making detailed decisions about what to cut and what to spare within the department.

"The expectation is the super committee will not touch the specifics of the defense budget," Sharp said. "The committee is going to use much more of a spreadsheet approach. They just need to make all the big numbers add up."

That means no specific decisions about weapons programs, troop levels or strategy.

"This is not a defense commission. This is a budget commission," Adams said. "Really their job is to set a number. That's why they were created."

While the committee will set the top line budget number, the rest of the appropriations process will remain intact. Congressional committees will decide the fate of individual programs, and the Pentagon will get its usual amount of input each fiscal year. Lobbyists will still lobby.

So the usual fight over the Pentagon budget will take place -- and with some powerful momentum working against the hawks.

"We are in a build down," Adams said. "It started two years ago and it is accelerating. It's not the first time we've done it. This would be the fifth since the end of the World War II."

That budget sea change -- coupled with the newfound willingness of some Republicans to chop the Pentagon's funding -- is what Kyl is up against.

Kyl finds himself in a tough spot. If the super committee fails to agree on trillions in budget savings, perhaps because of an unwillingness to compromise, a penalty of another $500 billion in Pentagon cuts will be triggered.